A thin film transistor (TFT) is a small amplifier tube formed by stacking fine and thin films, and is a three-terminal element including a gate, a source, and a drain.
Conventionally, a polycrystalline silicon film or an amorphous silicon film has typically been adopted as a channel layer of a thin film transistor. However, when a polycrystalline silicon film is used, electron scatter at the interface between crystal grains and the like limit electron mobility thereby to cause variation in transistor property. When an amorphous silicon film is used, electron mobility is very low and an element tends to deteriorate with time thereby to cause lower element reliability. In this regard, an oxide semiconductor has been attracting interests, which is higher in electron mobility than an amorphous silicon film and has less variation in transistor property than a polycrystalline silicon film.
There has been an active attempt to produce an electronic device on a flexible resin substrate in accordance with a low-energy production process such as a printing method or an application method. There is an advantage that a semiconductor layer can be patterned directly on the substrate in accordance with a printing method or an application method and no etching step is thus required for patterning.
As disclosed in Patent Documents 1 to 3, there has been an attempt to produce a coated flexible electronic device including a conductive polymer or an organic semiconductor, for example.